average IQ performances will be similar as well. Furthermore, some research
suggests that different ethnic groups, in response to their respective environ-
ments, are likely to develop different skills, not all of which are measured by IQ
tests.
Sex differences in cognition have been explored as well. Some hereditarian
approaches have claimed that the superior performance of the average male on
spacial and mathematical tests, and the superior performance of the average
female on verbal tests, reflect sex-linked genetic differences between the sexes.
Fluctuations in sex hormones are correlated with performance on just those
tasks on which the sexes are different. However, once again, the sex differences
may be largely attributable to environmental factors. I am personally impressed
with the research that shows that, with practice and feedback, women improve
as much as men do on spatial tasks. There is some admittedly controversial
evidence that sex differences in cognition are shrinking over time, possibly be-
cause of cultural changes made in recent years whereby more women are
encouraged to attend college and pursue careers in which mathematical and
spatial skills are important.
Certainly both the biological mechanisms put into place by the genes and the
environment invariably contribute to intellectual growth and individual differ-
ences. How could it be otherwise? A useful model of biology’s role in intelli-
gence must specify precisely how any given biological mechanism responds to
the various aspects of the environment in the course of intellectual develop-
ment. Given that controlled experiments are ethically and biologically impos-
sible, we may never completely understand the precise contributions that genes
and environmental factors make to individual intellectual differences.
Recommended Readings
Gould’s (1981)The Mismeasure of Manis a masterful and highly critical history
of the rise of the intelligence testing movement. An equally masterful compan-
ion piece is Tavris’s (1992)The Mismeasure of Woman, in which Tavris discusses
her thesis that male–female differences in human emotions and cognition are
greatly exaggerated. The case for important sex differences in human cognition
is provided in an interestingScientific Americanarticle by Kimura (1992). Gard-
ner published his six categories of intelligence theory in his (1983)Frames of
Mind, an exciting and wide-ranging book that has become highly influential in
educational circles. Certainly people interested in intelligence testing should
read Hernstein and Murray’s (1994) best-sellerThe Bell Curve,butpleaseread
along with it reviews ofThe Bell Curvewritten by experts in the field; a collec-
tion of such reviews can be found inThe Bell Curve Wars,editedbyFraser
(1995). A summary of what psychologists know and don’t know about intelli-
gence and intelligence testing can be found in a recentAmerican Psychologist
review paper by Neisser et al. (1996).
References
Anastasi, A. (1985). Reciprocal relations between cognitive and affective development: With impli-
cations for sex differences. In T. B. Sonderegger (Ed.),Psychology and gender(Nebraska Sym-
posium on Motivation, Vol. 32, pp. 1–35). Lincoln: University of Nebraska Press.
Anastasi, A. (1988).Psychological testing.NewYork:Macmillan.
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